- March 2019
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- The multi-objective optimal design of low-thrust multigravity-assist trajectories is formulated within the hybrid optimal control framework. A new automated solution strategy for this problem is proposed in this Paper based on a two-step algorithm. In the first step, the trajectory is assumed to be a generalized logarithmic spiral. A heuristic global search algorithm combined with nonlinear programming are in charge of optimizing the set of parameters defining the spirals as well as the number, sequence, and configuration of the gravity assists. In the second step, candidate solutions are regarded as initial guesses for a direct collocation method, in which the problem is transcribed into a nonlinear programming problem by discretization, considering the full dynamics and the complete set of constraints. The presented approach is tested on a rendezvous mission to the asteroid Ceres, allowing a Mars flyby, and on a flyby mission to Jupiter, allowing multiple flybys on different bodies. Pareto-optimal solutions in terms of time of flight and propellant mass consumed are obtained for both cases. Results outperform those found in the literature in terms of optimality while showing the effectiveness of the proposed methodology to generate quick performance estimates for preliminary studies and accurate solutions for the detailed design.
- multi-objective optimization; low-thrust optimal control; algorithms